Federal cybersecurity agencies warned on Tuesday that troves of new victims of the Medusa ransomware gang have been identified over the last year.

The Cybersecurity and Infrastructure Security Agency (CISA) and FBI updated an advisory on the group initially released in March 2025 — writing that as of April 2026, Medusa actors have hit more than 500 victims. CISA previously said 300 victims, many of which are in critical infrastructure sectors, were attacked as of 2025.

The group caused widespread outrage in April when it shut down the University of Mississippi Medical Center — Mississippi’s only children's hospital, only Level I trauma center, only Level IV neonatal intensive care unit and home to the state’s only organ transplant program.